In the case of vibrating machines for producing molded bodies by means of compacting granular raw mixtures in a vibratory manner, a charge of a hot mixture that is produced from petroleum coke and pitch as binding agent poured in the molding box that is to be fastened on the vibrating table is molded by means of vibratory compacting to form an anode block, namely to form the so-called raw green anode which is then baked in a furnace. In this case, the density and height of the block anode to be molded are subject to narrow tolerance limits. Once the molding box has been filled with the raw mixture charge, a cover weight is introduced, as a rule, into the molding box, said cover weight impacting or stamping at a certain impact frequency and impact intensity from above onto the mixture to be compacted. A fixed cover or vacuum cover, which surrounds the cover weight, is placed onto the top side of the filled molding box.
Once the block anode has been molded in the space between the top side of the vibrating table and the bottom side of the cover weight, the system of molding box/cover/cover weight, which is mounted so as to be able to oscillate and is exposed to the vertical oscillations of the vibratory drive, is lifted up from the vibrating table after the drive has been switched off and the pre-molded green block anode is pushed off the top side of the vibrating table to the side.
The fastening or clamping of the system of molding box/cover to the vibrating table, which can exert vertical oscillations at an amplitude of, for example, 4 to 5 mm during the vibrating operation, is exposed to enormous loads. As evidenced by the publication TMS published by Barry J. Welch of the Minerals, Metals & Materials Society, on the occasion of the 127th TMS Annual Meeting, San Antonio, Tex. held 15 on 15th-19th Feb. 1998 a lecture/paper by authors M. Bellstein and M. Spangehl was published, pages 746 and 747 of which showing a vibrating machine, the molding box and cover of which are to be detachably connected to the vibrating table by means of two clamping closures which are arranged at the sides opposite each other outside the molding box, in the following manner:
The known clamping closures are essentially assembled from the four components of pivot bracket, double-acting hydraulic pivot cylinder, two-armed rocker arm and resilient element. The pivot bracket which is pivotally mounted by way of its lower end on the vibrating table stands upright in its closed position. A two-armed rocker arm is pivotally connected to the upper end of the pivot bracket, the inner part of said rocker arm then pressing onto an outer part of the molding box or of the cover placed in position thereon, when the piston rod of the double-acting hydraulic pivot cylinder is extended and presses from underneath against the outer part of the two-armed rocker arm.
In order to hold the clamping closure securely in the closed position thereof, it has been known to allow the inner part of the two-armed rocker arm to lock on the molding box or on the cover thereof. To release the clamping closure it is necessary to move the rocker arm out of its locking position by means of its own retaining mechanism and to pivot the pivot bracket outward away from the molding box at an angle to the vertical, the piston rod of the associated hydraulic pivot cylinder being retracted in the open position of the clamping closure. The rocker arm retaining mechanism has been realized up to now by a long steel spiral tension spring which is arranged between pivot lever and associated hydraulic pivot cylinder, the upper end of which tension spring cooperates with the outer part of the two-armed rocker arm. It has been shown, however, that the oscillations, introduced by means of the vibratory drive and the vibrating table into the system of the vibrating machine that is held so as to be able to oscillate, can pass into the characteristic frequency range of the long tension springs, as a result of which strong oscillations are transmitted to the clamped tension springs and these can impair the service life of the tension springs.